% --- start of displayed preamble in the book ---
input featpost3Dplus2D
% --- end of displayed preamble in the book ---
defaultfont:="ptmr8r";
warningcheck:=0;
beginfig(1)
color gammacnt;
numeric newradius,radius,aux,i,numc,foc,lc;
path conepath, latpath;
pen thickp;

f:= (2,3,4);
viewcentr:= 1.5*(1,1,1);
Spread:= 200;
Shifts:= 300;
radius= 0.5;
numc= 9;
thickp= pencircle scaled .5;

pickup thickp;
tropicalglobe(numc,black,radius,blue);
for i=1 upto numc: % longitudes
 aux:= (i-1)*180/numc;
 gammacnt:=(cosd(aux),sind(aux),0);
 draw spatialhalfcircle
       (black,gammacnt,radius,true);
endfor;
endfig;
end;